Generally, power semiconductor devices refer to semiconductors able to control power, and enable the conversion or control of power over a range from ones of watts to gigawatts. Well-known examples of power semiconductor devices include a rectifying diode, a bipolar transistor, a thyristor, a GTO, a diac, a triac, a power MOSFET, an IGBT, an IPM (Intelligent Power Module), etc.
Among the power semiconductor devices, particularly useful is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) in order to reduce the size of a device because a JFET region is minimized or eliminated, thereby further lowering on-resistance (Ron) than when using a planar power MOSFET.
A conventional method of manufacturing a trench type power semiconductor device includes sequentially forming a first conductivity type low-concentration epitaxial layer and a guard ring region on a first conductivity type high-concentration semiconductor substrate.
Then, a second conductivity type body region is formed thereon, and an oxide film pattern, which is provided on the body region, is formed into a gate trench pattern using an etching mask. The oxide film pattern is etched, and a trench hole is formed in the epitaxial layer.
Subsequently, a sacrificial oxide film is grown and then removed, after which a gate oxide film is formed and the trench is filled with polysilicon which is doped to a high concentration.
Subsequently, photolithography and etching for forming a gate electrode are conducted, thus forming the gate. Further, a second conductivity type high-concentration source is formed through photolithography and ion implantation, and diffusion heat treatment is performed to define a channel region of the second conductivity type.
Finally, a first conductivity type high-concentration source is formed through photolithography and ion implantation, and an insulator is then formed thereon. Further, a contact hole is formed in the upper portion of the gate electrode and source region, and then, a metal process is carried out, thus completing the manufacture of a product. Typically, photolithography is conducted seven times.
Although this manufacturing method is advantageous because a device can be effectively manufactured to be smaller than a general vertical type MOSFET, it suffers in that the manufacturing technique is difficult to realize. Further, as competitiveness is increased, there is an urgent requirement to develop a way to simplify the manufacturing process.
To this end, various attempts have been made to simplify the process. In fact, however, it is not easy to simplify the process without deteriorating the properties of the device.